The stallion gave a self-satisfied nod. He'd shown her good. That'd teach her to mess with Rainbow. If she ever tried that again, he'd tear her a fat, new mouth with-his weapons! He let out a frustrated whinny and stomped his hoof. The sneaky pony had made off with his weapons!
Before he could roar at Miss M, a magenta hoof pushed his lips closed, a gentle voice caressing his ears. The wrath receded for a few precious moments. Goggles met emerald eyes, and he whined in confusion. He...he needed to go chase the naughty pony! Get his weapons back! Fight! Kill! Destroy!
And then a pair of foreleg wrapped around him, and pulled him into a curly, rainbow-colored wonderland. He caught one whiff of her mane, and his fight was over. The feral pony let out a soft nicker, wrapping her up in his forelegs and rubbing his muzzle in her luxurious locks. So delighted with the filly was he and so strong were the drugs, that he didn't even twitch as the needle pierced his neck. Shortly after the injection was snuck in, his affections grew sloppier, more sluggish, and Rainbow would hear the pleasured groans die out into gurgling sighs. His hind legs twitched and trembled, before finally buckling altogether, unable to hold his weight any longer.
Perhaps those stimulants were keeping him going a bit more than he let on.
[tldr: Sandy is about to chase after Miss M, when Rainbow distracts him as only his fillyfriend can. Caught up in the nuzzling and hugs, Sandy doesn't notice the injection at all. After the drugs are administered, he partially collapses in her forelegs.]
(Orzel: Are these new drugs an antidote to the stimulants, or really powerful depressants? It will actually make a difference on what happens next.)